Abstract [en]

Constructed stormwater wetlands (CSWs) are commonly used in Sweden and worldwide because of their high efficiency in urban stormwater management. However, questions have been raised about the long-term performance of CSWs. This study investigated the performance of a 19-year-old constructed wetland, which was designed to treat the stormwater from a 320-ha catchment located in the city of Växjö, southern Sweden. The system has not been maintained since its construction in 1994. The results of the present study were compared with results obtained from a previous study conducted by Växjö Municipality in 1997. The results showed that the CSW significantly reduced peak flows by 72%. High concentration reductions were found for Cd, Cr, Cu, Zn, Pb, TSS and TP (90, 89, 91, 90, 96, 96 and 86%, respectively). TN concentrations were reduced by 61%. The results indicated that lack of maintenance had no effect on the performance of wetland system during this long period of operation (19 years). In contrast, especially the removal of Cu and nitrogen was enhanced compared to 1997, which may be due to maturing of the system. The results show that CSWs are resilient systems, which (provided that design is sufficient) can work efficiently for at least two decades.